A Gatorade spokesman says the company did not produce the labels.
Gatorade announced in December that it was discontinuing its line of products featuring Woods.
The decision was first reported in a beverage industry magazine in November, before Woods admitted cheating on his wife, Elin.
The fake labels being discovered on Gatorade bottles in Denver feature a black and white photo of Tiger and Elin Woods along with the word "unfaithful" in Gatorade's distinctive block lettering.
Shoppers reported finding the mislabeled bottles at King Soopers and Safeway stores.
A 9NEWS employee visited a different store and found several more mislabeled bottles.
Shopper Robert Marlow said he found and purchased a bottle after friends told him they had found unusual bottles.
"I think it's pretty interesting," Marlow said.
"I want to know if it was an inside job. I want to know if it's a warehouse guy doing it," Marlow said. "I have no idea."
Marlow said he was unsure if he'd try to sell the bottle or add it to his collection of sports memorabilia.
"I don't think there will be much money in it," Marlow said.
He denied that he was behind the fake labels or knows who pulled the prank.
9NEWS contacted a man who identified himself as a temporary worker for Gatorade who said the company had sent a number of representatives into Denver-area stores on Sunday to remove the mislabeled products.
Each bottle seen by 9NEWS has a handwritten number on the bottom, indicating it is one of 100 made. The scribbling also includes a sort of signature, a letter surrounded by a circle.
"We believe this to be an isolated incident and are working with appropriate retailers and authorities to investigate," said Gatorade spokesman Pete Brace in a written statement.
"Our primary concern is the safety of our consumers and the integrity of our products," Brace wrote.
The bottles do not appear to be opened or tampered with apart from the new label.
Federal consumer protection laws prohibit tampering with labels.
The Federal Anti-Tampering Act makes it a crime to render a label materially false or misleading if the intent is to cause "serious injury to the business of any person."
If you have information about this story, or would like to suggest another story idea, you may e-mail 9NEWS reporter Kyle Clark.
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